ST_Different-PolarDB(PolarDB)-阿里云帮助中心

Returns the part of geometry A that does not intersect geometry B.

Syntax

geometry ST_Difference(geometry geomA, geometry geomB)

Parameter	Description
`geomA`	The source geometry. The result is always a portion of this geometry.
`geomB`	The geometry to subtract from `geomA`.

Input order matters. ST_Difference(A, B) always returns a portion of A.
If geomA is completely contained within geomB, the function returns an empty geometry.
GeometryCollection inputs are not supported.
For 3D geometries, the function computes the difference using X and Y coordinates only. Z coordinate values in the result are preserved from the input geometries (z coordinates are not deleted).

The following example returns the segment of the first line that does not overlap with the second line:

SELECT ST_AsText(
  ST_Difference(
    'LINESTRING(0 0,0 2)'::geometry,
    'LINESTRING(0 1,0 3)'::geometry
  )
);

Result:

      st_astext
---------------------
 LINESTRING(0 0,0 1)
(1 row)